package com.condado.newsletter.service

import com.condado.newsletter.model.ParsedAiResponse
import com.fasterxml.jackson.annotation.JsonIgnoreProperties
import com.fasterxml.jackson.annotation.JsonProperty
import org.slf4j.LoggerFactory
import org.springframework.beans.factory.annotation.Value
import org.springframework.stereotype.Service
import org.springframework.web.client.RestClient

/**
 * Calls the OpenAI Chat Completions API to generate email content.
 * Returns a [ParsedAiResponse] with the extracted subject and body.
 */
@Service
class AiService(
    private val restClient: RestClient,
    @Value("\${openai.api-key}") private val apiKey: String,
    @Value("\${openai.model:gpt-4o}") private val model: String
) {
    private val log = LoggerFactory.getLogger(javaClass)

    /**
     * Sends [prompt] to the OpenAI API and returns the parsed subject + body.
     * @throws [AiServiceException] on API errors.
     * @throws [AiParseException] if the response format is unexpected.
     */
    fun generate(prompt: String): ParsedAiResponse {
        val rawText = try {
            val request = ChatRequest(
                model = model,
                messages = listOf(ChatMessage(role = "user", content = prompt))
            )
            val json = restClient.post()
                .uri("https://api.openai.com/v1/chat/completions")
                .header("Authorization", "Bearer $apiKey")
                .body(request)
                .retrieve()
                .body(String::class.java)
                ?: throw AiServiceException("OpenAI returned an empty response")

            extractContent(json)
        } catch (e: AiServiceException) {
            throw e
        } catch (e: Exception) {
            log.error("OpenAI API call failed: ${e.message}", e)
            throw AiServiceException("OpenAI API call failed: ${e.message}", e)
        }

        return parseResponse(rawText)
    }

    /**
     * Parses the raw AI output into a [ParsedAiResponse].
     * Expected format:
     * ```
     * SUBJECT: <subject line>
     * BODY:
     * <email body>
     * ```
     */
    fun parseResponse(raw: String): ParsedAiResponse {
        val lines = raw.trim().lines()

        val subjectLine = lines.firstOrNull { it.startsWith("SUBJECT:", ignoreCase = true) }
            ?: throw AiParseException("AI response missing SUBJECT line. Raw response: $raw")

        val bodyStart = lines.indexOfFirst { it.trim().equals("BODY:", ignoreCase = true) }
        if (bodyStart == -1) throw AiParseException("AI response missing BODY: section. Raw response: $raw")

        val subject = subjectLine.replaceFirst(Regex("^SUBJECT:\\s*", RegexOption.IGNORE_CASE), "").trim()
        val body = lines.drop(bodyStart + 1).joinToString("\n").trim()

        return ParsedAiResponse(subject = subject, body = body)
    }

    // ── internal JSON helpers ────────────────────────────────────────────────

    private fun extractContent(json: String): String {
        val mapper = com.fasterxml.jackson.databind.ObjectMapper()
        val tree = mapper.readTree(json)
        return tree["choices"]?.firstOrNull()?.get("message")?.get("content")?.asText()
            ?.replace("\\n", "\n")
            ?: throw AiServiceException("Unexpected OpenAI response structure: $json")
    }

    @JsonIgnoreProperties(ignoreUnknown = true)
    data class ChatRequest(val model: String, val messages: List<ChatMessage>)

    @JsonIgnoreProperties(ignoreUnknown = true)
    data class ChatMessage(val role: String, val content: String)
}